1. Field of the Invention
The present invention relates generally to the field of pharmacology and cancer treatment. Specifically, the present invention provides formulations and methods for small particle aerosol delivery by inhalation of aqueous dispersions of liposomes carrying anti-cancer drugs to the respiratory tract.
2. Description of the Related Art
Small particle liposome aerosol treatment consists of lipid-soluble or water-soluble anti-cancer drugs incorporated into liposomes, which are administered from aqueous dispersions in a jet nebulizer (see U.S. Pat. No. 5,049,388). Aerosols of 1-3 xcexcm mass median aerodynamic diameter, generated upon nebulization, enable targeted delivery onto surfaces of the respiratory tract. The deposited liposomes subsequently release drug locally within the lung or into the blood circulation with delivery to extra-pulmonary tissue. If the drug is lipid soluble, it will associate with the lipid molecules in a manner specific to the lipid employed, the anti-cancer drug employed and possibly it may be modified further by various soluble constituents which may be included in the suspending aqueous medium. Such soluble constituents may include buffering salts and possibly inositol to enhance the synthesis and secretion of surfactant phospholipid in lung tissue and to minimize respiratory distress already present or that which might result from the aerosol treatment (Hallman, M., et al. Inositol Supplementation in Premature Infants with Respiratory Distress Syndrome, N. Eng. J. Med. 1992 326:1233-1239).
If the drug is water soluble, it may be incorporated by appropriate procedures in aqueous vesicles that exist in concentric spaces between lipid bilayers (lamellae) of the multilamellar liposome. Unilamellar liposomes may be prepared; however, their capacity to entrap either lipid-soluble or water-soluble drugs is diminished since entrapment is restricted to one central vesicle. Additionally, lipid complexes of various sizes can be used.
Nebulization shears liposomes and other lipid complexes to sizes readily discharged from the nozzle of the nebulizer. Liposomes and other lipid complexes up to several microns in diameter are typically sheared to diameters of less than 500 nm, and may be considerably smaller than that depending on the operating characteristics of the nebulizer and other variables. Shearing of water-soluble drugs contained in liposomes or complexes will release appreciable amounts of the water soluble compound, perhaps 50 percent. This is not a contraindication to their use, but it means that two forms of the drug preparation is administered, and the effect includes the therapeutic effect that would be produced by both forms if either form had been given alone. Many other details of liposome aerosol treatment are described in U.S. Pat. No. 5,049,388. Moreover, it is also possible to incorporate more than one drug in a aerosol liposome treatment, either by mixing different drug-containing liposomes, or by using liposomes wherein the drugs have been combined and incorporated together into liposomes.
The prior art is deficient in formulations and methods for small particle aerosol delivery of aqueous dispersions of liposomes or lipid complexes containing anti-cancer drugs. The present invention fulfills this long-standing need and desire in the art.
The small particle liposome or lipid complex aerosol compounds and methods of treatment of the present invention involve lipid-soluble or water-soluble anti-cancer drugs incorporated into liposomes or other lipid complexes. These drug-carrying lipids then are administered in aqueous dispersions from a jet nebulizer. The present invention demonstrates that speedier and more efficient systemic absorption of drug is actualized after pulmonary administration by aerosol than is actualized by intramuscular or oral administration.
One object of the present invention is to provide a method for treating cancer, comprising the step of delivering, via small particle aerosol, aqueous dispersions of anti-cancer drugs to the respiratory tract of an individual in need of such treatment. Examples of anticancer drugs available for use in this embodiment of the invention include, but are not limited to, 20-S-camptothecin, 9-nitro-camptothecin, 9-amino-camptothecin, 10, 11-methylenedioxy-camptothecin, taxol, taxol-A, mitotane, methotrexate, mercaptopurine, lomustine, interferon, 5-fluorouracil and etopiside. In a more preferred embodiment of this object, the anti-cancer drug is selected from the group consisting of 20-S-camptothecin, 9-nitro-camptothecin, 9-amino-camptothecin, 10, 11-methylenedioxy-camptothecin and taxol. Additionally, in a preferred embodiment of the present objective, the delivery of the anticancer drug is performed by a jet nebulizer.
In another object of the present invention, there is provided a lipid complex or liposome for delivery of anticancer drugs via small particle aerosols comprising an anticancer drug and a lipid, wherein the anticancer drug is at a concentration not exceeding about 10% of the total volume of the preparation and a ratio of the anticancer drug to the suitable solvent is in the range of about 1:1 to about 1:200, preferably in a range of about 1:10 to about 1:100, and most preferably in a range of about 1:10 to about 1:50 (wt:wt) of the preparation. One specific embodiment of this object includes 9-nitro-camptothecin and dilauroylphosphatidylcholine in a ratio of about 1:10 to 1:50 wt:wt; with a particularly preferred embodiment having a 9-nitro-camptothecin and dilauroylphosphatidylcholine of about 1:50 wt:wt. In another embodiment, there is provided a liposome for delivery of anticancer drugs via small particle aerosols comprising Taxol and dilauroylphosphatidylcholine in a ratio of about 1:30 wt:wt.
In yet another embodiment of the present invention, there is provided a liposome produced by the following steps: dissolving a lipid-soluble anticancer drug in a solvent suitable for dissolving the anticancer drug to produce dissolved anticancer drug; adding the dissolved anticancer drug to a dissolved lipid suitable for formulation and delivery of drugs by aerosol to produce a solution, wherein the dissolved anticancer drug is at a concentration not exceeding about 10% of the total volume of the solution and a ratio of the anticancer drug to the lipid is in the range of about 1:1 to about 1:200, preferably in a range of about 1:10 to about 1:100, and most preferably in a range of about 1:10 to about 1:50 (wt:wt) of the solution; and freezing and lyophilizing the solution. At this point, the solution may be stored frozen for later use or dissolved in sterile water for use, producing a suspension, wherein the concentration of the anticancer drug in the sterile water in the suspension is no more than about 5.0 mg/ml.
A preferred embodiment of the above object provides liposomal preparations of 20-S-camptothecin (CPT), 9-nitrocamptothecin (9-NC) and other lipid soluble camptothecin derivatives, produced by the following steps: preparing concentrated stock solutions of said 20-S-camptothecin (CPT), 9-nitrocamptothecin (9-NC) or other-lipid soluble camptothecin derivatives and lipids in compatible solvents; adding appropriate volumes of the 20-S-camptothecin (CPT), 9-nitrocamptothecin (9-NC) or other-lipid soluble camptothecin derivative and lipid concentrated stock solutions to a volume of t-butanol to form a second solution, wherein a concentration of said 20-S-camptothecin (CPT), 9-nitrocamptothecin (9-NC) and other lipid soluble camptothecin derivatives does not exceed 10% of said second solution and wherein a ratio of drug to lipid is in the range of about 1:1 to about 1:200, preferably in a range of about 1:10 to about 1:100, and most preferably in a range of about 1:10 to about 1:50 (wt:wt) in said second solution; freezing said second solution; and lyophilizing said second solution to produce a powder preparation. At this point, the powder preparation may be stored frozen for later use or dissolved in sterile water producing a suspension, wherein a concentration of said anticancer drug in said suspension is no more than about 5 mg/ml.
A more particular embodiment provides liposomes produced by the following steps: preparing a concentrated stock solutions of anticancer drug, for example 100 mg CPT in 1 ml t-butanol or 100 mg 9-NC in DMSO, preparing a stock solution of lipid, for example, 100 mg DLPC in 1 ml butanol; adding appropriate volumes of said concentrated stock solutions to a volume of t-butanol to form a second solution wherein a final volume is about 10 ml, a volume of DMSO, if any, does not exceed 10% (vol:vol) of said final volume, a concentration of anticancer drug does not exceed 10% (wt:wt) of the total volume, and wherein a ratio of drug to lipid is in a range of about 1:1 to about 1:200, preferably in a range of about 1:10 to about 1:100, and most preferably in a range of about 1:10 to about 1:50 (wt:wt); freezing said second solution; and lyophilizing said frozen solution to produce a powder preparation. Tthe powder preparation may then be stored frozen for later use or dissolved in sterile water producing a suspension. Generally, the concentration of the anticancer drug in the suspension is no more than about 5 mg/ml.
Another preferred embodiment of the object above provides a liposome produced by the following steps: mixing taxol with synthetic alpha lecithin: dilauroylphosphatidylcholine; dissolving the taxol-DLPC in t-butanol to produce a preparation; and freezing and lyophilizing the preparation. Liposomes are produced by adding sterile, pure water at a temperature above 25xc2x0 C., wherein the final concentration of taxol to dilauroylphosphatidylcholine is about 1:1 to about 1:200, preferably in a range of about 1:10 to about 1:100, and most preferably in a range of about 1:25 to about 1:40 (wt:wt). In addition to alpha lecithin, other natural or synthetic lecithins may be used, including but not limited to egg yolk phosphatidylcholine, hydrogenated soybean phosphatidylcholine, dimyristophosphatidylcholine, diolyeolyl-dipalmitoyleolylphospha-tidylcholine and dipalmitoyl phosphatidylcholine.
The efficiency of incorporation of 9-NC and other camptothecin derivatives and anticancer drugs into liposomes can be tested by layering an aqueous dispersion of lyophilized drug-liposome preparation over a Percoll(trademark) gradient and centrifuging. Unincorporated drug collects at the bottom of the tube, but drug incorporated into liposomes collects at the interface between the Percoll gradient and the water phase. One qualitative test of incorporation efficiency is the observation of drug crystals when the dispersion of drug-liposomes are examined by microscopy under polarized light. Other methods are also available, for example, analytical HPLC methods can be used to quantitatively assess non-encapsulated, crystalized drug.
Other and further aspects, features, and advantages of the present invention will be apparent from the following description of the presently preferred embodiments of the invention. These embodiments are given for the purpose of disclosure.